338 
A. E. Verrill — North American Cephalopods. 
the posterior aorta divides into three large arteries: one of these (o) 
is situated in the median plane, and crossing the branchial cavity in a 
curved line along the edge of the thin median membrane, supplies the 
ventral and lateral portions of the mantle, sending branches both for- 
ward and backward ; the other two main branches (o' o") diverge as 
they go backward and supply the caudal fins and adjacent parts of 
the mantle. The anterior aorta ( ao ) arises from the right anterior 
corner of the heart, and goes forward to the head, on the right side of 
the median line, by the side of the oesophagus, giving oft' from its sides 
various small branches. Xear its origin it is somewhat bulbous. 
The first branch, the gastric artery, arising not far from its origin, 
sends a branch to the renal organs, and running backward over the 
dorsal side of the heart, ramifies over both lobes of the stomach. 
During its passage through the substance of the liver, and along 
the groove on its dorsal side, the aorta gives off several branches 
which supply that organ with blood, while one artery, of consider- 
able size, emerges from the posterio-dorsal side of the liver and 
supplies the muscles of the neck ; others go out from the anterior 
part of the liver, laterally and ventrally, to various parts of the head. 
Ten large branches go to the arms, one running through the center 
of each to the tip, sending oft’ numerous lateral branches to the suckers 
and other parts. Other branches supply the various organs of the 
head. A small artery (fig. 2, go) arises from the anterior side of the 
heart, and turning backward, supplies the spermary (t). The large 
efferent vessels (branch io-cardiac) from the gills (bo) enter the 
anterio-lateral corners of the heart, their dilated basal portions serv- 
ing as auricles. 
The branchial auricles (au), situated just behind the bases of the 
gills, are nearly globular, with a small, rounded, whitish elevation 
on the free posterior end ; dorsal ly they receive the blood from the 
saccular divisions of the anterior and posterior vente-cavae (vc, vc ') 
and from the veins (y, vc) coming from the lateral portions of the 
mantle, behind the gills ; and they give oft’ the large afferent vessels 
(bv) which go to and run along the dorsal side of the gills. 
The anterior vena-cava (vc) receives the venous blood from a large 
cephalic venous sinus, which surrounds the pharynx, at the bases of 
the arms,* and is connected with another large sinus situated at the 
* The greater part of the venous system can be easily injected by inserting a canula 
into this sinus, through the fold of the buccal membranes between the bases of the 
arms and the jaws, or between the outer and inner buccal membranes. It can also be 
easily injected through the vena-cava in the lower side of the head. 
